La Crosse virus infection of Aedes triseriatus (Diptera: Culicidae) ovaries before dissemination of virus from the midgut.

La Crosse (LAC) virus is efficiently transmitted transovarially by the mosquito Aedes triseriatus (Say). To determine the time course and tropisms of LAC virus infection of ovaries, immunofluorescent antibody staining, in situ hybridization, and reverse transcription-polymerase chain reaction techniques were used to detect viral antigen and RNA in the ovaries. LAC virus was detected in the ovaries (presumably in calyx tissues) by all 3 assays at day 2 after infection and before dissemination from the midgut on day 6. Apparently, ovaries can become infected by mechanisms other than by dissemination of virus from a midgut infection. By days 8-14 after infection, virus analytes became detectable in many tissues within the ovary including follicular epithelium, oocytes, nurse cells, and calyx, reflecting the remarkable host parasite relationship between LAC virus and its mosquito vector.